There are known control systems for straight slot direct current motor actuators, as shown in FIG. 1, which use a control system based on three feedback loops providing information on the angular position of the motor, the angular rotation speed and the current strength, the angular position and the current strength being measured by sensors. In the example of FIG. 1, the system comprises three measurement sensors, namely a sensor CP for measuring the angular position of the motor M, a sensor CV for measuring the angular rotation speed of the motor M, and a sensor CC for measuring the current strength in the motor M. These three sensors transmit their measurements along three respective feedback loops, namely a position feedback loop BRP, a speed feedback loop BRV, and a current feedback loop BRC.
The basic set point which is calculated is a set position of the motor M. The measurement θ transmitted by the position sensor CP, by means of the position feedback loop BRP, is subtracted from this set position by a first subtractor SOUS—1, and the result is transmitted to a corrector of the angular position of the motor CORRP, of a known type, which delivers at its output a set angular rotation speed for the motor. The measurement Ω, transmitted by the angular rotation speed sensor CV by means of the speed feedback loop BRV, is subtracted from this set angular rotation speed by a second subtractor SOUS—2, and the result is transmitted to a corrector of the angular rotation speed of the motor CORRV, of a known type, which delivers at its output a set motor current strength. The measurement Im, transmitted by the current sensor CC by means of the current feedback loop, is subtracted from this set motor current by a third subtractor SOUS—3, and the result is transmitted to a known motor current corrector CORRC, which delivers at its output a voltage Um which is applied to the motor M.
The cost of the sensors is high in a feedback control system of this type, notably the cost of the sensor CV for measuring the angular rotation speed Ω of the motor M.